/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.flink.table.runtime.arrow.serializers;

import org.apache.flink.annotation.Internal;
import org.apache.flink.table.runtime.arrow.ArrowReader;
import org.apache.flink.table.runtime.arrow.ArrowUtils;
import org.apache.flink.table.runtime.arrow.ArrowWriter;
import org.apache.flink.table.types.logical.RowType;

import org.apache.arrow.memory.BufferAllocator;
import org.apache.arrow.vector.VectorSchemaRoot;
import org.apache.arrow.vector.ipc.ArrowStreamReader;
import org.apache.arrow.vector.ipc.ArrowStreamWriter;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

/**
 * The base class ArrowSerializer which will serialize/deserialize RowType data to/from arrow bytes.
 *
 * @param <T> type of the input elements.
 */
@Internal
public abstract class ArrowSerializer<T> {

	static {
		ArrowUtils.checkArrowUsable();
	}

	/**
	 * The input RowType.
	 */
	protected final RowType inputType;

	/**
	 * The output RowType.
	 */
	protected final RowType outputType;

	/**
	 * Allocator which is used for byte buffer allocation.
	 */
	private transient BufferAllocator allocator;

	/**
	 * Reader which is responsible for deserialize the Arrow format data to the Flink rows.
	 */
	private transient ArrowReader<T> arrowReader;

	/**
	 * Reader which is responsible for convert the execution result from
	 * byte array to arrow format.
	 */
	private transient ArrowStreamReader arrowStreamReader;

	/**
	 * Container that holds a set of vectors for the input elements
	 * to be sent to the Python worker.
	 */
	transient VectorSchemaRoot rootWriter;

	/**
	 * Writer which is responsible for serialize the input elements to arrow format.
	 */
	private transient ArrowWriter<T> arrowWriter;

	/**
	 * Writer which is responsible for convert the arrow format data into byte array.
	 */
	private transient ArrowStreamWriter arrowStreamWriter;

	public ArrowSerializer(
		RowType inputType,
		RowType outputType) {
		this.inputType = inputType;
		this.outputType = outputType;
	}

	public void open(InputStream bais, OutputStream baos) throws Exception {
		allocator = ArrowUtils.getRootAllocator().newChildAllocator("allocator", 0, Long.MAX_VALUE);
		arrowStreamReader = new ArrowStreamReader(bais, allocator);

		rootWriter = VectorSchemaRoot.create(ArrowUtils.toArrowSchema(inputType), allocator);
		arrowWriter = createArrowWriter();
		arrowStreamWriter = new ArrowStreamWriter(rootWriter, null, baos);
		arrowStreamWriter.start();
	}

	public int load() throws IOException {
		arrowStreamReader.loadNextBatch();
		VectorSchemaRoot root = arrowStreamReader.getVectorSchemaRoot();
		if (arrowReader == null) {
			arrowReader = createArrowReader(root);
		}
		return root.getRowCount();
	}

	public T read(int i) {
		return arrowReader.read(i);
	}

	public void write(T element) {
		arrowWriter.write(element);
	}

	public void close() throws Exception {
		arrowStreamWriter.end();
		arrowStreamReader.close();
		rootWriter.close();
		allocator.close();
	}

	/**
	 * Creates an {@link ArrowWriter}.
	 */
	public abstract ArrowWriter<T> createArrowWriter();

	public abstract ArrowReader<T> createArrowReader(VectorSchemaRoot root);

	/**
	 * Forces to finish the processing of the current batch of elements.
	 * It will serialize the batch of elements into one arrow batch.
	 */
	public void finishCurrentBatch() throws Exception {
		arrowWriter.finish();
		arrowStreamWriter.writeBatch();
		arrowWriter.reset();
	}
}
